Longitudinally pumped laser diode pumped lasers, generally, have relied on laser diode pump sources which generally are low power devices. As a consequence, the output power from a ring laser, or standing wave laser, has been limited by the power available from the pumping laser diodes. Combinations of more than one pumping sources have met with limited success since the problems associated with overpumping and alignment of more than one pumping source has unduly complicated the design and compromised efficiency.
Methods of obtaining higher power end-pumped lasers have involved combining laser diodes or combining gain elements such as that disclosed in the single gain-element ring laser entitled "A Single Frequency Nd:YAG Ring Laser Pumped by Laser Diodes" by Richard Scheps et al. which appears in IEEE Journal of Quantum Electronics, Vol. 26, No. 3, March 1990. This design uses two single-stripe one-watt laser diodes which form a single beam that is focused on the exterior face of a Nd:YAG rod. Single longitudinal mode performance for CW operation and single-transverse-multi-longitudinal-mode output performance for Q-switched operation were demonstrated in a combination of compact side and high efficiency. A design restraint on the use of this single gain-element ring laser is that its diode-pumped output power was limited by the available highest-power 11 laser diodes which were available for pumping. A typical recent attempt to combine laser diodes and gain-elements is set forth in the above reference co-pending application. However, this method fails to provide for a more maximum output, since it does not allow for the pumping of each of the gain elements along multiple paths.
Thus there is a continuing need in the state of the art for a diode pumping configuration for one or more gain elements in a ring laser having the capability for increased output power due to a more efficient optical pumping thereof.